A major hurdle to advances in treating cancer is the relative lack of agents that can selectively target the cancer, while sparing normal tissue. For example, radiation therapy and surgery, which generally are localized treatments, can cause substantial damage to normal tissue in the treatment field, resulting in scarring and, in severe cases, loss of function of the normal tissue. Chemotherapy, in comparison, which generally is administered systemically, can cause substantial damage to organs such as bone marrow, mucosae, skin and the small intestine, which undergo rapid cell turnover and continuous cell division. As a result, undesirable side effects such as nausea, loss of hair and drop in blood cell count occur as a result of systemically treating a cancer patient with chemotherapeutic agents. Such undesirable side effects often limit the amount of a treatment that can be administered. Thus, cancer remains a leading cause of patient morbidity and death.
Tumor malignancies accounts for 85% cancer mortality that was responsible for 23% of all deaths in US. Current approaches for the treatment of tumor malignancies with established agents and with the new targeted agents used alone and in combination are limited, in part, by inability to deliver cytotoxic agents selectively to the tumor tissue in sufficient concentrations critical for tumor cell kill that translate into meaningful and durable responses.
Cancers metastasize through tumor vasculature, which is diverse in both its cellular and molecular compositions, exhibiting variation in the type of cells that line the vessels and their complement of cell-surface receptors. Blood vessels are one type of tumor vasculature, and archetypal blood vessels are entirely lined with endothelial cells. Tumor blood vessels also can be mosaic or lined by both endothelial and tumor cells, while other vessels are formed entirely from tumor cells. Lymphatic vessels, which also occur within several tumor types, are a second type of tumor vasculature. The lymphatic vasculature is an important route for the spreading of cancer, and animal experiments have shown a positive correlation between metastasis and the number of lymphatic vessels in and around a tumor. The development of vascular-specific tools for cancer diagnosis and/or therapy has been hindered by the paucity of targets.
Accordingly, there exists a need for improved compositions and methods for treating cancer.